package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;


import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor {
    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException, IntrospectionException, InstantiationException, InvocationTargetException {
        // 1.注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        // 2.获取sql语句
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        // 3.获取预处理对象 preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        // 4.设置参数

        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterClass = getClassType(parameterType);

        List<ParameterMapping> mappingList = boundSql.getMappingList();
        for (int i = 0; i < mappingList.size(); i++) {
            ParameterMapping parameterMapping = mappingList.get(i);
            String content = parameterMapping.getContent();

            // 反射
            // 获取属性对象
            Field declaredField = parameterClass.getDeclaredField(content);
            // 设置暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1,o);

        }

        // 5.执行sql
        ResultSet resultSet = preparedStatement.executeQuery();

        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        // 返回的集合
        ArrayList<Object> objects = new ArrayList<>();

        // 6.封装返回结果集
        while (resultSet.next()){
            Object o = resultTypeClass.newInstance();
            // 元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for(int i=1; i <= metaData.getColumnCount();i++){
                // 字段名
                String columnName = metaData.getColumnName(i);
                // 字段的值
                Object value = resultSet.getObject(columnName);

                // 使用反射或内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
            objects.add(o);
        }
        return (List<E>) objects;
    }


    @Override
    public Integer executeUpdate(Configuration configuration, MappedStatement mappedStatement, Object... params) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException, InstantiationException, IntrospectionException, InvocationTargetException {
        // 1.注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        // 2.获取sql语句
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        // 3.获取预处理对象 preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        // 4.设置参数
        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterClass = getClassType(parameterType);

        List<ParameterMapping> mappingList = boundSql.getMappingList();
        for (int i = 0; i < mappingList.size(); i++) {
            ParameterMapping parameterMapping = mappingList.get(i);
            String content = parameterMapping.getContent();
            // 反射
            // 获取属性对象
            Field declaredField = parameterClass.getDeclaredField(content);
            // 设置暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1,o);
        }

        // 5.执行sql
        Integer result = preparedStatement.executeUpdate();
        return result;
    }

    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
        if(parameterType != null){
            Class<?> aClass = Class.forName(parameterType);
            return aClass;
        }
        return null;
    }



    /**
     * 完成对{}的解析
     * 1.将#{}用问号代替
     * 2.对解析出的#{}里的值进行存储
     * @param sql
     * @return
     */
    BoundSql getBoundSql(String sql){
        // 标记处理类:配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        String parseSql = genericTokenParser.parse(sql);
        // #{}里面解析出来的名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        BoundSql boundSql = new BoundSql(parseSql,parameterMappings);
        return boundSql;
    }
}
